I think
FramerT, that while production numbers shouldn't be the only factor in determining a tanks worth it is certainly a necessary factor. The Sherman was cheaper to build, maintain and repair that almost any other vehicles. This allowed the troops using the vehicle to get more active service out of their vehicles while in the field. German AFV's, while generally technically superior to the Sherman, required much more cost, machining and upkeep. What this means is that given the exact same amount of starting resources, the US had more servicable tanks for longer periods in the field. When you evaluate a tank you must evaluate the entire length of it's life. Mass production alone doesn't cut it, but when you can do more with less from the outset, I think it matters.
That said, in direct tank vs. tank combat, I'd rather be a tiger crewman than a M4 crewman, any day of the week.
